Little is known about clinical predictors of aortic dissection in children and young adults, although many children with certain genetic conditions have significant aortic dilation, and aortic dissection has been reported as early as 6 months of age. Due to the paucity of data available in children and young adults, management of these patients is widely variable, and optimal timing of prophylactic aortic surgery is unknown, despite frequent cardiac imaging to assess aortic size. Standard measures of risk in aortic dilation such as absolute aortic dimensions and rate of aortic dilation may not apply in growing children, and there is little data to show at what threshold to manifest concern. Vascular tortuosity is a common finding in connective tissue disorders, especially due to single gene mutations. We have identified a new potential imaging biomarker, the vertebral artery tortuosity index (VTI), that in pilot research appears to be an independent indicator of risk for aortic dissection and other adverse cardiovascular events in children and young adults. The studies in this proposal will begin to address major deficiencies in the current knowledge regarding aortic disease risk in the young population. Ultimately, we plan to follow both cohorts to collect further longitudinal data on this population. The long term goal of the proposed research is to create an online tool for practitioners and parents that uses clinical, genetic, and imaging data to assess the prognosis for aortic events and informs the management as to aortic imaging frequency, medication use, activity restrictions, and optimal timing of surgery to prevent life-threatening AD